This invention relates to the developing of light sensitive plates. The invention is particularly concerned with an improved process and apparatus which can be used e.g. for automatically developing relatively rigid, generally metallic positive or negative plates covered with a light-sensitive photopolymerisable layer on at least one side, used e.g. in offset printing or typographical or flexographical printing.
The exposure of the light-sensitive layer of a plate or sheet to suitable radiation has the effect of hardening or softening the parts affected by this radiation. The developing process has the function of eliminating the parts which will not be used for printing by means of a suitable solvent. Some plates can be developed by simply being soaked in a bath; other plates require brushing.
In the case of offset plates, it is found that there are a large number of manufacturers producing plates with the composition and hardness of the sensitive layers varying substantially from one manufacturer to another.
Thus one object of the invention is to provide the possibility of a versatile automatic process and apparatus capable of developing a wider range of the commercially available plates having a sensitive layer. The process and apparatus should be adaptable to the different formats of the plates and be capable of treating the various types of sensitive layers without impairing them and without requiring any complex adjustment.
A further problem with known systems is that some developing baths oxidise in the air. It is therefore very desirable to provide developing apparatus wherein the bath is protected from contact with the air, in spite of the diversity of conventional processes which are used depending on the nature of the sensitive layers, for example employing simple soaking, spraying under pressure, a friction sponge system and so forth.